1. Field of the Invention
The present invention relates to electrostatographic members such as, for example, fuser, transfer and transfix members, having a surface release layer comprised of a nitrile-silicone rubber or elastomer.
2. Discussion of Related Art
In a typical electrostatographic reproducing apparatus such as an electrophotographic imaging system using a photoreceptor, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of a developer containing colorants such as pigments or dyes. One type of developer used in such printing machines is a liquid developer comprising a liquid carrier having toner particles dispersed therein. Generally, the toner is made up of resin and a suitable colorant such as a dye or pigment. Conventional charge director compounds may also be present. The liquid developer material is brought into contact with the electrostatic latent image and the colored toner particles are deposited thereon in image configuration.
The developed toner image recorded on the imaging member is then transferred either directly to an image receiving substrate such as paper or first to an intermediate transfer member and then to an image receiving substrate.
The toner particles may be transferred by heat and/or pressure to an intermediate transfer member, or more commonly, the toner particles may be electrostatically transferred to the intermediate transfer member by means of an electrical potential between the imaging member and the intermediate transfer member. After the toner has been transferred to the intermediate transfer member, it is then transferred to the image receiving substrate, for example by contacting the substrate with the toner image on the intermediate transfer member under heat and/or pressure.
Intermediate transfer members enable high throughput at modest process speeds. In four-color photocopier systems, the intermediate transfer member also improves registration of the final color toner image. In such systems, the four component colors of cyan, yellow, magenta and black may be synchronously developed onto one or more imaging members and transferred in registration onto an intermediate transfer member at a transfer station.
The toner particles in image configuration are ultimately transferred to the image receiving substrate. The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner to be bonded firmly to the support.
Several approaches to thermal fusing of toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat can be applied by heating one or both of the rolls, plate members, or belt members. Fusing of the toner particles occurs when the proper combination of heat, pressure, and/or contact for the optimum time period are provided. The balancing of these variables to bring about the fusing of the toner particles is well known in the art, and can be adjusted to suit particular machines or process conditions.
During the operation of one fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between a pair of rolls, plates, belts, or combination thereof. The concurrent transfer of heat and the application of pressure in the nip effects the fusing of the toner image onto the support.
It is important that the toner particles are able to have nearly complete transfer from any intermediate members used, and also not exhibit any transfer to fuser members (referred to as toner offset) used. To ensure these results, the surface layers of these members should be comprised of materials having low surface energies, have temperature stability and resistance, be insulative to semiconductive and be smooth.
Surface layers of these types of members in an electrostatographic device thus typically have comprised silicone rubber or fluoroelastomers as a preferred material. For example, conventional materials known in the art as useful for intermediate transfer member surfaces include silicone rubbers, fluorocarbon elastomers such as are available under the trademark VITON from E. I. du Pont de Nemours and Co., polyvinyl fluoride such as available under the tradename TEDLAR also available from E. I. du Pont de Nemours and Co, various fluoropolymers such as polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA-TEFLON), fluorinated ethylenepropylene copolymer (FEP), other TEFLON-like materials, and the like and mixtures thereof.
U.S. Pat. No. 6,037,092, incorporated herein by reference in its entirety, discloses a fuser member comprising a substrate and at least one layer thereover, the layer comprising a crosslinked product of a liquid composition which comprises (a) a fluorosilicone, (b) a crosslinking agent, and (c) a thermal stabilizing agent comprising a reaction product of (i) a cyclic unsaturated-alkyl-group-substituted polyorganosiloxane, (ii) a linear unsaturated-alkyl-group-substituted polyorganosiloxane, and (iii) a metal acetylacetonate or metal oxalate compound.
U.S. Pat. No. 5,991,590, incorporated herein by reference in its entirety, describes a transfer member having a substrate, an outer silicone rubber layer, and a silicone polymer release agent material, wherein the release agent material is a polydimethyl siloxane cationic liquid emulsion.
U.S. Pat. No. 5,846,643 describes a fuser member for use in an electrostatographic printing machine has at least one layer of an elastomer composition comprising a silicone elastomer and a mica-type layered silicate, the silicone elastomer and mica-type layered silicate forming a delaminated nanocomposite with silicone elastomer inserted among the delaminated layers of the mica-type layered silicate.
U.S. Pat. No. 5,864,740 discloses a thermally stabilized silicone liquid composition and a toner fusing system using the thermally stabilized silicone liquid as a release agent, wherein the thermally stabilized silicone liquid contains a silicone liquid and a thermal stabilizer composition (including a reaction product from at least a polyorganosiloxane and a platinum metal compound (Group VIII compound) such as a ruthenium compound, excluding platinum).
U.S. Pat. No. 4,150,181 discloses a contact fuser assembly and method for preventing toner offset on a heated fuser member in an electrostatic reproducing apparatus which includes a base member coated with a solid, abrasion resistant material such as polyimide, poly(amide-imides), poly(imide-esters), polysulfones, and aromatic polyamides. The fuser member is coated with a thin layer of polysiloxane fluid containing low molecular weight fluorocarbon. Toner offset on the heated fuser member is prevented by applying the polysiloxane fluid containing fluorocarbon to the solid, abrasion resistant surface of the fuser member.
U.S. Pat. No. 4,711,818 discloses a thermally conductive dry release fuser member and fusing method for use in electrostatic reproducing machines without the application of a release agent. The fuser member comprises a base support member and a thin deformable layer of a composition coated thereon, the composition comprising the crosslinked product of a mixture of at least one addition curable vinyl terminated or vinyl pendant polyfluoroorganosiloxane, filler, heat stabilizer, a crosslinking agent, and a crosslinking catalyst.
U.S. Pat. Nos. 5,464,703 and 5,563,202 disclose a fuser member useful for heat fixing an electrographic toner to a substrate, a composition of matter, and its preparation method. The fuser member has a core and a base cushion layer overlying the core. The base cushion layer includes a crosslinked poly(dimethylsiloxanefluoroalkylsiloxane) elastomer that has tin oxide particles dispersed therein in a concentration of from 20 to 40 percent of the total volume of the base cushion layer.
Silicone rubbers are widely used in fusing subsystems, largely because they can be modified to optimum fusing properties. Desirable physical properties in fusing materials include thermal conductivity, hardness, and toughness. However, one disadvantage of using silicone rubbers is that silicone rubbers swell in various solvents and in silicone oils. In current release agent technology, silicone oils are commonly used, but because of the swelling of silicone rubber in the oil, it is often necessary to coat the silicone fuser rolls with a fluoropolymer. Fluorosilicones that will resist swelling and possess the preferred physical properties for fusing are also available, but fluorosilicones are unstable at high temperatures (for example, over 300xc2x0 F.), can release hazardous materials, and also are an environmentally unfriendly material.
Accordingly, while known compositions and processes are suitable for their intended purposes, a need remains for improved materials with better solvent resistance. Further, a need remains for a fuser, pressure, transfer and/or transfix member surface layer that does not result in significant swelling of the outer layer of the member during operation. In particular, as presently employed silicone rubbers swell upon exposure to hydrocarbon liquids such as found in most liquid developers, which swelling adversely affects the operation and quality output from the device, a need remains for improved materials for these members.
It is one object of the present invention to develop a material for use as a surface release layer of an electrostatographic member that exhibits improved solvent and swelling resistance.
It is a further object of the present invention to develop a fuser, pressure, transfer and/or transfix member in which the surface layer of the member exhibits low surface energy, temperature stability and resistance, smoothness, appropriate electrical conductivity, long life and solvent and swelling resistance to hydrocarbons.
These and other objects are achieved herein by the present invention, which comprises a member for use in a copying device comprising at least a substrate and thereon a surface layer comprised of a nitrile-silicone rubber or elastomer. The member may have any form, including a belt, plate or drum configuration. The member may be used in the copying device as a fuser member, a pressure member, a transfer member or a transfix member. It can also be utilized in printer, xerography or direct marking applications.